Auer H E, Sun M, Greulick M
Physiol Chem Phys. 1979;11(1):9-22.
The pH-induced dissociation of cytochrome c oxidase from dimer to protomer has been studied in the pH range 7 to 11. Findings are as follows: The heme A:copper ratio is 1.0 at both pH 7.4 and 10.6. The relative enzymatic activity is preserved at all pH values at which the dimer or protomer are found. The fraction of protomer, determined from sedimentation velocity profiles, increases from 0 to 1 as the pH is raised. The absorption and circular dichroism spectra in the Soret region change in ways indicating that the contributions of cytochrome a in typical cytochrome aa3 spectral patterns are progressively lost as pH increases. At pH values more alkaline than the above, denaturation occurs. The fraction of protomer, and certain parameters defined to quantitate the changes in spectral form, exhibit similar pH profiles for a given preparation; but these concerted changes occur over different pH ranges for different preparations. Nevertheless the optical parameters are linearly correlated with the fraction of protomer for each preparation. It is concluded that the spectral properties of the dimer and the protomer are intrinsic attributes of each species and are not directly affected by changes in ambient pH.
在pH值7至11的范围内，研究了pH诱导的细胞色素c氧化酶从二聚体解离为单体的过程。研究结果如下：在pH 7.4和10.6时，血红素A与铜的比例均为1.0。在发现二聚体或单体的所有pH值下，相对酶活性均得以保留。根据沉降速度曲线确定的单体比例随pH升高从0增加到1。索雷特区域的吸收光谱和圆二色光谱发生变化，表明随着pH升高，典型细胞色素aa3光谱模式中细胞色素a的贡献逐渐丧失。在比上述pH值更碱性的条件下，会发生变性。对于给定的制剂，单体比例以及用于定量光谱形式变化的某些参数呈现相似的pH曲线；但这些协同变化在不同制剂的不同pH范围内发生。然而，对于每种制剂，光学参数与单体比例呈线性相关。得出的结论是，二聚体和单体的光谱特性是每种物质的固有属性，不受环境pH变化的直接影响。
